无法将 const char 转换为 char

将文本中的每个字母替换为字母表中 n 个字符之后的字母的程序。编译时出现错误 cannot convert const char * to char* (swears at input_text)

#include "pch.h"
#include <iostream>
using namespace std;

int main()
{
    char *input_text;
    char *output_text;
    input_text = "bla bla";
    int n = 5;
    int count = 0;
    for (int i = 0; input_text[i] != 0; i++)
    {
        count++;
    }
    int input_text_lenght = count;
    output_text = new char[input_text_lenght];
    for (int k = 0; k < input_text_lenght; k++)
    {
        output_text[k] = input_text[k] + n;
    }
    cout << "input_text ... " << input_text << endl;

    cout << "output_text ... " << output_text << endl;
    delete[] output_text;
    return 0;
}